NAME

NAME
Perl::ToPerl6 - Critique Perl source code for best-practices.

SYNOPSIS
use Perl::ToPerl6;
my $file = shift;
my $mogrify = Perl::ToPerl6->new();
my @transformations = $mogrify->transform($file);
print @transformations;

DESCRIPTION
Perl::ToPerl6 is an extensible framework for creating and applying
coding standards to Perl source code. Essentially, it is a static source
code analysis engine. Perl::ToPerl6 is distributed with a number of
Perl::ToPerl6::Transformer modules that attempt to enforce various
coding guidelines. Most Transformer modules are based on Damian Conway's
book Perl Best Practices. However, Perl::ToPerl6 is not limited to PBP
and will even support Transformers that contradict Conway. You can
enable, disable, and customize those Polices through the Perl::ToPerl6
interface. You can also create new Transformer modules that suit your
own tastes.

For a command-line interface to Perl::ToPerl6, see the documentation for
perlmogrify. If you want to integrate Perl::ToPerl6 with your build
process, Test::Perl::ToPerl6 provides an interface that is suitable for
test programs. Also, Test::Perl::ToPerl6::Progressive is useful for
gradually applying coding standards to legacy code. For the ultimate
convenience (at the expense of some flexibility) see the mogrification
pragma.

If you'd like to try Perl::ToPerl6 without installing anything, there is
a web-service available at <http://perlmogrify.com>. The web-service
does not yet support all the configuration features that are available
in the native Perl::ToPerl6 API, but it should give you a good idea of
what it does.

Also, ActivePerl includes a very slick graphical interface to
Perl-ToPerl6 called "perlmogrify-gui". You can get a free community
edition of ActivePerl from <http://www.activestate.com>.

INTERFACE SUPPORT
This is considered to be a public class. Any changes to its interface
will go through a deprecation cycle.

CONSTRUCTOR
"new( [ -profile => $FILE, -severity => $N, -theme => $string, -include
=> \@PATTERNS, -exclude => \@PATTERNS, -top => $N, -only => $B,
-profile-strictness => $PROFILE_STRICTNESS_{WARN|FATAL|QUIET}, -force =>
$B, -verbose => $N ], -color => $B, -pager => $string, -allow-unsafe =>
$B, -mogrification-fatal => $B)"
"new()"
Returns a reference to a new Perl::ToPerl6 object. Most arguments
are just passed directly into Perl::ToPerl6::Config, but I have
described them here as well. The default value for all arguments can
be defined in your .perlmogrifyrc file. See the "CONFIGURATION"
section for more information about that. All arguments are optional
key-value pairs as follows:

-profile is a path to a configuration file. If $FILE is not defined,
Perl::ToPerl6::Config attempts to find a .perlmogrifyrc
configuration file in the current directory, and then in your home
directory. Alternatively, you can set the "PERLMOGRIFY" environment
variable to point to a file in another location. If a configuration
file can't be found, or if $FILE is an empty string, then all
Transformers will be loaded with their default configuration. See
"CONFIGURATION" for more information.

-severity is the minimum severity level. Only Transformer modules
that have a severity greater than $N will be applied. Severity
values are integers ranging from 1 (least severe transformations) to
5 (most severe transformations). The default is 5. For a given
"-profile", decreasing the "-severity" will usually reveal more
Transformer transformations. You can set the default value for this
option in your .perlmogrifyrc file. Users can redefine the severity
level for any Transformer in their .perlmogrifyrc file. See
"CONFIGURATION" for more information.

If it is difficult for you to remember whether severity "5" is the
most or least restrictive level, then you can use one of these named
values:

SEVERITY NAME ...is equivalent to... SEVERITY NUMBER
--------------------------------------------------------
-severity => 'gentle' -severity => 5
-severity => 'stern' -severity => 4
-severity => 'harsh' -severity => 3
-severity => 'cruel' -severity => 2
-severity => 'brutal' -severity => 1

The names reflect how severely the code is mogrified: a "gentle"
mogrification reports only the most severe transformations, and so
on down to a "brutal" mogrification which reports even the most
minor transformations.

-theme is special expression that determines which Transformers to
apply based on their respective themes. For example, the following
would load only Transformers that have a 'bugs' AND 'core' theme:

my $mogrify = Perl::ToPerl6->new( -theme => 'bugs && core' );

Unless the "-severity" option is explicitly given, setting "-theme"
silently causes the "-severity" to be set to 1. You can set the
default value for this option in your .perlmogrifyrc file. See the
"POLICY THEMES" section for more information about themes.

-include is a reference to a list of string @PATTERNS. Transformer
modules that match at least one "m/$PATTERN/ixms" will always be
loaded, irrespective of all other settings. For example:

my $mogrify = Perl::ToPerl6->new(-include => ['layout'] -severity => 4);

This would cause Perl::ToPerl6 to apply all the "CodeLayout::*"
Transformer modules even though they have a severity level that is
less than 4. You can set the default value for this option in your
.perlmogrifyrc file. You can also use "-include" in conjunction with
the "-exclude" option. Note that "-exclude" takes precedence over
"-include" when a Transformer matches both patterns.

-exclude is a reference to a list of string @PATTERNS. Transformer
modules that match at least one "m/$PATTERN/ixms" will not be
loaded, irrespective of all other settings. For example:

my $mogrify = Perl::ToPerl6->new(-exclude => ['strict'] -severity => 1);

This would cause Perl::ToPerl6 to not apply the "RequireUseStrict"
and "ProhibitNoStrict" Transformer modules even though they have a
severity level that is greater than 1. You can set the default value
for this option in your .perlmogrifyrc file. You can also use
"-exclude" in conjunction with the "-include" option. Note that
"-exclude" takes precedence over "-include" when a Transformer
matches both patterns.

-single-transformer is a string "PATTERN". Only one transformer that
matches "m/$PATTERN/ixms" will be used. Transformers that do not
match will be excluded. This option has precedence over the
"-severity", "-theme", "-include", "-exclude", and "-only" options.
You can set the default value for this option in your .perlmogrifyrc
file.

-top is the maximum number of Transformations to return when ranked
by their severity levels. This must be a positive integer.
Transformations are still returned in the order that they occur
within the file. Unless the "-severity" option is explicitly given,
setting "-top" silently causes the "-severity" to be set to 1. You
can set the default value for this option in your .perlmogrifyrc
file.

-only is a boolean value. If set to a true value, Perl::ToPerl6 will
only choose from Transformers that are mentioned in the user's
profile. If set to a false value (which is the default), then
Perl::ToPerl6 chooses from all the Transformers that it finds at
your site. You can set the default value for this option in your
.perlmogrifyrc file.

-profile-strictness is an enumerated value, one of
"$PROFILE_STRICTNESS_WARN" in Perl::ToPerl6::Utils::Constants (the
default), "$PROFILE_STRICTNESS_FATAL" in
Perl::ToPerl6::Utils::Constants, and "$PROFILE_STRICTNESS_QUIET" in
Perl::ToPerl6::Utils::Constants. If set to
"$PROFILE_STRICTNESS_FATAL" in Perl::ToPerl6::Utils::Constants,
Perl::ToPerl6 will make certain warnings about problems found in a
.perlmogrifyrc or file specified via the -profile option fatal. For
example, Perl::ToPerl6 normally only "warn"s about profiles
referring to non-existent Transformers, but this value makes this
situation fatal. Correspondingly, "$PROFILE_STRICTNESS_QUIET" in
Perl::ToPerl6::Utils::Constants makes Perl::ToPerl6 shut up about
these things.

-force is a boolean value that controls whether Perl::ToPerl6
observes the magical "## no mogrify" annotations in your code. If
set to a true value, Perl::ToPerl6 will analyze all code. If set to
a false value (which is the default) Perl::ToPerl6 will ignore code
that is tagged with these annotations. See "BENDING THE RULES" for
more information. You can set the default value for this option in
your .perlmogrifyrc file.

-verbose can be a positive integer (from 1 to 11), or a literal
format specification. See Perl::ToPerl6::Transformation for an
explanation of format specifications. You can set the default value
for this option in your .perlmogrifyrc file.

-unsafe directs Perl::ToPerl6 to allow the use of Transformers that
are marked as "unsafe" by the author. Such transformers may compile
untrusted code or do other nefarious things.

-color and -pager are not used by Perl::ToPerl6 but is provided for
the benefit of perlmogrify.

-mogrification-fatal is not used by Perl::ToPerl6 but is provided
for the benefit of mogrification.

-color-severity-highest, -color-severity-high, -color-severity-
medium, -color-severity-low, and -color-severity-lowest are not used
by Perl::ToPerl6, but are provided for the benefit of perlmogrify.
Each is set to the Term::ANSIColor color specification to be used to
display transformations of the corresponding severity.

-files-with-transformations and -files-without-transformations are
not used by Perl::ToPerl6, but are provided for the benefit of
perlmogrify, to cause only the relevant filenames to be displayed.

METHODS
"transform( $source_code )"
Runs the $source_code through the Perl::ToPerl6 engine using all the
Transformers that have been loaded into this engine. If $source_code
is a scalar reference, then it is treated as a string of actual Perl
code. If $source_code is a reference to an instance of
PPI::Document, then that instance is used directly. Otherwise, it is
treated as a path to a local file containing Perl code. This method
returns a list of Perl::ToPerl6::Transformation objects for each
transformation of the loaded Transformers. The list is sorted in the
order that the Transformations appear in the code. If there are no
transformations, this method returns an empty list.

"apply_transform( -transformer => $transformer_name, -params =>
\%param_hash )"
Creates a Transformer object and loads it into this ToPerl6. If the
object cannot be instantiated, it will throw a fatal exception.
Otherwise, it returns a reference to this ToPerl6.

-transformer is the name of a Perl::ToPerl6::Transformer subclass
module. The 'Perl::ToPerl6::Transformer' portion of the name can be
omitted for brevity. This argument is required.

-params is an optional reference to a hash of Transformer
parameters. The contents of this hash reference will be passed into
to the constructor of the Transformer module. See the documentation
in the relevant Transformer module for a description of the
arguments it supports.

" transformers() "
Returns a list containing references to all the Transformer objects
that have been loaded into this engine. Objects will be in the order
that they were loaded.

" config() "
Returns the Perl::ToPerl6::Config object that was created for or
given to this ToPerl6.

" statistics() "
Returns the Perl::ToPerl6::Statistics object that was created for
this ToPerl6. The Statistics object accumulates data for all files
that are analyzed by this ToPerl6.

FUNCTIONAL INTERFACE
For those folks who prefer to have a functional interface, The
"transform" method can be exported on request and called as a static
function. If the first argument is a hashref, its contents are used to
construct a new Perl::ToPerl6 object internally. The keys of that hash
should be the same as those supported by the "Perl::ToPerl6::new()"
method. Here are some examples:

use Perl::ToPerl6 qw(transform);

# Use default parameters...
@transformations = transform( $some_file );

# Use custom parameters...
@transformations = transform( {-severity => 2}, $some_file );

# As a one-liner
%> perl -MPerl::ToPerl6=transform -e 'print transform(shift)' some_file.pm

None of the other object-methods are currently supported as static
functions. Sorry.

CONFIGURATION
Most of the settings for Perl::ToPerl6 and each of the Transformer
modules can be controlled by a configuration file. The default
configuration file is called .perlmogrifyrc. Perl::ToPerl6 will look for
this file in the current directory first, and then in your home
directory. Alternatively, you can set the "PERLMOGRIFY" environment
variable to explicitly point to a different file in another location. If
none of these files exist, and the "-profile" option is not given to the
constructor, then all the modules that are found in the
Perl::ToPerl6::Transformer namespace will be loaded with their default
configuration.

The format of the configuration file is a series of INI-style blocks
that contain key-value pairs separated by '='. Comments should start
with '#' and can be placed on a separate line or after the name-value
pairs if you desire.

Default settings for Perl::ToPerl6 itself can be set before the first
named block. For example, putting any or all of these at the top of your
configuration file will set the default value for the corresponding
constructor argument.

severity = 3 #Integer or named level
only = 1 #Zero or One
force = 0 #Zero or One
verbose = 4 #Integer or format spec
top = 50 #A positive integer
theme = (pbp || security) && bugs #A theme expression
include = NamingConventions ClassHierarchies #Space-delimited list
exclude = Variables Modules::RequirePackage #Space-delimited list
mogrification-fatal = 1 #Zero or One
color = 1 #Zero or One
allow-unsafe = 1 #Zero or One
pager = less #pager to pipe output to

The remainder of the configuration file is a series of blocks like this:

[Perl::ToPerl6::Transformer::Category::TransformerName]
severity = 1
set_themes = foo bar
add_themes = baz
maximum_transformations_per_document = 57
arg1 = value1
arg2 = value2

"Perl::ToPerl6::Transformer::Category::TransformerName" is the full name
of a module that implements the transformer. The Transformer modules
distributed with Perl::ToPerl6 have been grouped into categories
according to the table of contents in Damian Conway's book Perl Best
Practices. For brevity, you can omit the 'Perl::ToPerl6::Transformer'
part of the module name.

"severity" is the level of importance you wish to assign to the
Transformer. All Transformer modules are defined with a default severity
value ranging from 1 (least severe) to 5 (most severe). However, you may
disagree with the default severity and choose to give it a higher or
lower severity, based on your own coding philosophy. You can set the
"severity" to an integer from 1 to 5, or use one of the equivalent
names:

SEVERITY NAME ...is equivalent to... SEVERITY NUMBER
----------------------------------------------------
gentle 5
stern 4
harsh 3
cruel 2
brutal 1

The names reflect how severely the code is mogrified: a "gentle"
mogrification reports only the most severe transformations, and so on
down to a "brutal" mogrification which reports even the most minor
transformations.

"set_themes" sets the theme for the Transformer and overrides its
default theme. The argument is a string of one or more
whitespace-delimited alphanumeric words. Themes are case-insensitive.
See "POLICY THEMES" for more information.

"add_themes" appends to the default themes for this Transformer. The
argument is a string of one or more whitespace-delimited words. Themes
are case- insensitive. See "POLICY THEMES" for more information.

"maximum_transformations_per_document" limits the number of
Transformations the Transformer will return for a given document. Some
Transformers have a default limit; see the documentation for the
individual Transformers to see whether there is one. To force a
Transformer to not have a limit, specify "no_limit" or the empty string
for the value of this parameter.

The remaining key-value pairs are configuration parameters that will be
passed into the constructor for that Transformer. The constructors for
most Transformer objects do not support arguments, and those that do
should have reasonable defaults. See the documentation on the
appropriate Transformer module for more details.

Instead of redefining the severity for a given Transformer, you can
completely disable a Transformer by prepending a '-' to the name of the
module in your configuration file. In this manner, the Transformer will
never be loaded, regardless of the "-severity" given to the
Perl::ToPerl6 constructor.

A simple configuration might look like this:

#--------------------------------------------------------------
# I think these are really important, so always load them

[TestingAndDebugging::RequireUseStrict]
severity = 5

[TestingAndDebugging::RequireUseWarnings]
severity = 5

#--------------------------------------------------------------
# I think these are less important, so only load when asked

[Variables::ProhibitPackageVars]
severity = 2

[ControlStructures::ProhibitPostfixControls]
allow = if unless # My custom configuration
severity = cruel # Same as "severity = 2"

#--------------------------------------------------------------
# Give these transformers a custom theme. I can activate just
# these transformers by saying `perlmogrify -theme larry`

[Modules::RequireFilenameMatchesPackage]
add_themes = larry

[TestingAndDebugging::RequireTestLables]
add_themes = larry curly moe

#--------------------------------------------------------------
# I do not agree with these at all, so never load them

[-NamingConventions::Capitalization]
[-ValuesAndExpressions::ProhibitMagicNumbers]

#--------------------------------------------------------------
# For all other Transformers, I accept the default severity,
# so no additional configuration is required for them.

For additional configuration examples, see the perlmogrifyrc file that
is included in this examples directory of this distribution.

Damian Conway's own Perl::ToPerl6 configuration is also included in this
distribution as examples/perlmogrifyrc-conway.

THE POLICIES
A large number of Transformer modules are distributed with
Perl::ToPerl6. They are described briefly in the companion document
Perl::ToPerl6::TransformerSummary and in more detail in the individual
modules themselves. Say ""perlmogrify -doc PATTERN"" to see the perldoc
for all Transformer modules that match the regex "m/PATTERN/ixms"

There are a number of distributions of additional transformers on CPAN.
If Perl::ToPerl6 doesn't contain a transformer that you want, some one
may have already written it. See the "SEE ALSO" section below for a list
of some of these distributions.

POLICY THEMES
Each Transformer is defined with one or more "themes". Themes can be
used to create arbitrary groups of Transformers. They are intended to
provide an alternative mechanism for selecting your preferred set of
Transformers. For example, you may wish disable a certain subset of
Transformers when analyzing test programs. Conversely, you may wish to
enable only a specific subset of Transformers when analyzing modules.

The Transformers that ship with Perl::ToPerl6 have been broken into the
following themes. This is just our attempt to provide some basic logical
groupings. You are free to invent new themes that suit your needs.

THEME DESCRIPTION
--------------------------------------------------------------------------
core All transformers that ship with Perl::ToPerl6
pbp Transformers that come directly from "Perl Best Practices"
bugs Transformers that that prevent or reveal bugs
maintenance Transformers that affect the long-term health of the code
cosmetic Transformers that only have a superficial effect
complexity Transformers that specificaly relate to code complexity
security Transformers that relate to security issues
tests Transformers that are specific to test programs

Any Transformer may fit into multiple themes. Say "perlmogrify -list" to
get a listing of all available Transformers and the themes that are
associated with each one. You can also change the theme for any
Transformer in your .perlmogrifyrc file. See the "CONFIGURATION" section
for more information about that.

Using the "-theme" option, you can create an arbitrarily complex rule
that determines which Transformers will be loaded. Precedence is the
same as regular Perl code, and you can use parentheses to enforce
precedence as well. Supported operators are:

Operator Alternative Example
-----------------------------------------------------------------
&& and 'pbp && core'
|| or 'pbp || (bugs && security)'
! not 'pbp && ! (portability || complexity)'

Theme names are case-insensitive. If the "-theme" is set to an empty
string, then it evaluates as true all Transformers.

BENDING THE RULES
Perl::ToPerl6 takes a hard-line approach to your code: either you comply
or you don't. In the real world, it is not always practical (nor even
possible) to fully comply with coding standards. In such cases, it is
wise to show that you are knowingly violating the standards and that you
have a Damn Good Reason (DGR) for doing so.

To help with those situations, you can direct Perl::ToPerl6 to ignore
certain lines or blocks of code by using annotations:

require 'LegacyLibaray1.pl'; ## no mogrify
require 'LegacyLibrary2.pl'; ## no mogrify

for my $element (@list) {

## no mogrify

$foo = ""; #Violates 'ProhibitEmptyQuotes'
$barf = bar() if $foo; #Violates 'ProhibitPostfixControls'
#Some more evil code...

## use mogrify

#Some good code...
do_something($_);
}

The "## no mogrify" annotations direct Perl::ToPerl6 to ignore the
remaining lines of code until a "## use mogrify" annotation is found. If
the ""## no mogrify"" annotation is on the same line as a code
statement, then only that line of code is overlooked. To direct
perlmogrify to ignore the ""## no mogrify"" annotations, use the
"--force" option.

A bare "## no mogrify" annotation disables all the active Transformers.
If you wish to disable only specific Transformers, add a list of
Transformer names as arguments, just as you would for the "no strict" or
"no warnings" pragmas. For example, this would disable the
"ProhibitEmptyQuotes" and "ProhibitPostfixControls" transformers until
the end of the block or until the next "## use mogrify" annotation
(whichever comes first):

## no mogrify (EmptyQuotes, PostfixControls)

# Now exempt from ValuesAndExpressions::ProhibitEmptyQuotes
$foo = "";

# Now exempt ControlStructures::ProhibitPostfixControls
$barf = bar() if $foo;

# Still subjected to ValuesAndExpression::RequireNumberSeparators
$long_int = 10000000000;

Since the Transformer names are matched against the "## no mogrify"
arguments as regular expressions, you can abbreviate the Transformer
names or disable an entire family of Transformers in one shot like this:

## no mogrify (NamingConventions)

# Now exempt from NamingConventions::Capitalization
my $camelHumpVar = 'foo';

# Now exempt from NamingConventions::Capitalization
sub camelHumpSub {}

The argument list must be enclosed in parentheses and must contain one
or more comma-separated barewords (e.g. don't use quotes). The "## no
mogrify" annotations can be nested, and Transformers named by an inner
annotation will be disabled along with those already disabled an outer
annotation.

Some Transformers like "Subroutines::ProhibitExcessComplexity" apply to
an entire block of code. In those cases, the "## no mogrify" annotation
must appear on the line where the transformation is reported. For
example:

sub complicated_function { ## no mogrify (ProhibitExcessComplexity)
# Your code here...
}

Transformers such as "Documentation::RequirePodSections" apply to the
entire document, in which case transformations are reported at line 1.

Use this feature wisely. "## no mogrify" annotations should be used in
the smallest possible scope, or only on individual lines of code. And
you should always be as specific as possible about which Transformers
you want to disable (i.e. never use a bare "## no mogrify"). If
Perl::ToPerl6 complains about your code, try and find a compliant
solution before resorting to this feature.

THE Perl::ToPerl6 PHILOSOPHY
Coding standards are deeply personal and highly subjective. The goal of
Perl::ToPerl6 is to help you write code that conforms with a set of best
practices. Our primary goal is not to dictate what those practices are,
but rather, to implement the practices discovered by others. Ultimately,
you make the rules -- Perl::ToPerl6 is merely a tool for encouraging
consistency. If there is a transformer that you think is important or
that we have overlooked, we would be very grateful for contributions, or
you can simply load your own private set of transformers into
Perl::ToPerl6.

EXTENDING THE MOGRIFIER
The modular design of Perl::ToPerl6 is intended to facilitate the
addition of new Transformers. You'll need to have some understanding of
PPI, but most Transformer modules are pretty straightforward and only
require about 20 lines of code. Please see the Perl::ToPerl6::DEVELOPER
file included in this distribution for a step-by-step demonstration of
how to create new Transformer modules.

If you develop any Transformer modules, feel free to add a pull request
on GitHub, <http://github.com/drforr/Perl-Mogrify.git>.

PREREQUISITES
Perl::ToPerl6 requires the following modules:

B::Keywords

Config::Tiny

Exception::Class

File::HomeDir

File::Spec

File::Spec::Unix

File::Which

IO::String

List::MoreUtils

List::Util

Module::Pluggable

PPI

Pod::PlainText

Pod::Select

Pod::Usage

Readonly

Scalar::Util

String::Format

Task::Weaken

Term::ANSIColor

Text::ParseWords

version

CONTACTING THE DEVELOPMENT TEAM
You are encouraged to subscribe to the mailing list; send a message to
<mailto:[email protected]>. To prevent spam, you
may be required to register for a user account with Tigris.org before
being allowed to post messages to the mailing list. See also the mailing
list archives at
<http://perlmogrify.tigris.org/servlets/SummarizeList?listName=users>.
At least one member of the development team is usually hanging around in
<irc://irc.perl.org/#perlmogrify> and you can follow Perl::ToPerl6 on
Twitter, at <https://twitter.com/perlmogrify>.

BUGS
Scrutinizing Perl code is hard for humans, let alone machines. If you
find any bugs, particularly false-positives or false-negatives from a
Perl::ToPerl6::Transformer, please submit them at
"/github.com/Perl-ToPerl6 /Perl-ToPerl6/issues" in https:. Thanks.

CREDITS
Adam Kennedy - For creating PPI, the heart and soul of Perl::ToPerl6.

Damian Conway - For writing Perl Best Practices, finally :)

Chris Dolan - For contributing the best features and Transformer
modules.

Andy Lester - Wise sage and master of all-things-testing.

Elliot Shank - The self-proclaimed quality freak.

Giuseppe Maxia - For all the great ideas and positive encouragement.

and Sharon, my wife - For putting up with my all-night code sessions.

Thanks also to the Perl Foundation for providing a grant to support
Chris Dolan's project to implement twenty PBP transformers.
<http://www.perlfoundation.org/april_1_2007_new_grant_awards>

AUTHOR
Jeffrey Goff <[email protected]>

AUTHOR Emeritus
Jeffrey Ryan Thalhammer <[email protected]>

COPYRIGHT
Copyright (c) 2015 Jeffrey Goff. All rights reserved.

This program is free software; you can redistribute it and/or modify it
under the same terms as Perl itself. The full text of this license can
be found in the LICENSE file included with this module.